In recent years, it has been frequently seen that old buildings, or machines and electronic devices degraded with time fail. Many of these degradation failures occur due to mechanical wear or cracks generated by long-time use. Such wear degradation or cracks generate unnecessary vibration. Thus, in order to predict and prevent grave accidents caused by degradation or failures, a sensor for detecting vibration generated due to wear degradation or cracks is used in many cases.
Vibrations generated from an object to be detected of water piping which is a vibration source or the like include not only vibration in a direction perpendicular to a front surface of the object to be detected but also vibrations in various directions. Thus, to predict and prevent degradation, detecting vibrations in various directions is needed. For example, as a technology for detecting vibration accelerations in three axial directions, there is developed a technology using a piezoelectric acceleration sensor as described in Patent Literature 1 (PTL1) or an acceleration sensor using MEMS (Micro Electro Mechanical Systems) as described in Patent Literature 2 (PTL2).
Patent Literature 3 (PTL3) discloses a method for detecting external forces in X and Y axis directions orthogonal to a detecting direction (Z axis) based on detection outputs different from one another in phase and detected by three vibration sensors each for detecting vibration acceleration in one axial direction.